A construction crew preparing to pour concrete for the new Transbay Transit Center discovered an old but well-preserved human skeleton - later determined to be that of an American Indian - Tuesday morning.

The discovery begins a process in which an Indian designee will determine how the remains, whose age has not been determined, should be handled.

Workers discovered the skeleton at a depth of 60 feet on the east end of the construction site near Fremont Street about 8 a.m., said Stephanie Reichin, a spokeswoman for the Transbay Joint Powers Authority, which is building the transit hub project.

They immediately contacted the San Francisco medical examiner's office and the project's architects, who confirmed that the remains were those of an Indian. They left the remains in place and cordoned off a protected area in a 100-foot radius.

Officials also contacted the state Native American Heritage Commission, as required. The commission will appoint an Indian, probably within days, to serve as "most likely descendant" and determine whether the remains should be removed or left on the site and buried. The commission could not be reached for comment Tuesday afternoon.

Work on the $1.9 billion Transbay Transit Center is continuing outside the protected area, Reichin said, and the process of determining how the remains are handled is not expected to cause significant delays.